1. Field of the Invention
The present invention relates to an image forming method and an image forming apparatus using a treatment liquid and a recording ink.
2. Description of the Related Art
In an inkjet recording system, means for improving image density by pre-coating a recording medium with a treatment liquid and bringing a water-based recording ink into contact with the treatment liquid to thereby agglutinate the colorant is commonly known. As a component for agglutinating the colorant in the water-based recording ink, polyvalent metal salts and cationic resins are known. However, problems remain in the conventional art as to storage stability and various safety properties of the treatment liquid itself.
For example, there are proposals for adding an amino acid such as glycine and alanine to the treatment liquid (see Japanese Patent Application Laid-Open (JP-A) No. 2012-187771 and Japanese Patent (JP-B) Nos. 4194531 and 3799253). However, according to these proposals, there are problems in storage stability of the treatment liquid, when the treatment liquid is used in a system configured to apply the treatment liquid under open air.
A water-soluble organic solvent such as glycerin is generally used as a humectant of the treatment liquid. However, although no particular significant problem arises under hermetical conditions of a certain degree such as in a head, water evaporation is heavy in a system in which coating of the treatment liquid is performed under open air, which causes great changes in the properties of the treatment liquid. Further, a highly hydrophilic organic solvent is generally used in order to be dissolved in water, which is the main component. This consequently fosters curling of a recording medium.